TechSat 21 and Revolutionizing Space Missions using Microsatellites

The Air Force Research Laboratory (AFRL) TechSat 21 flight experiment demonstrates a formation of three microsatellites flying in formation to operate as a “virtual satellite.” X-band transmit and receive payloads on each of the satellites form a large sparse aperture system. The satellite formation can be configured to optimize such varied missions as radio frequency (RF) sparse aperture imaging, precision geolocation, ground moving target indication (GMTI), single-pass digital terrain elevation data (DTED), electronic protection, single-pass interferometric synthetic aperture radar (IF-SAR), and high data-rate, secure communications. Benefits of such a microsatellite formation over single large satellites include unlimited aperture size and geometry, greater launch flexibility, higher system reliability, easier system upgrade, and low cost mass production. Key research has focused on the areas of formation flying and sparse aperture signal processing and been sponsored and guided by the Air Force Office of Scientific Research (AFOSR). The TechSat 21 Program Preliminary Design Review (PDR) was held in April 2001 and incorporated the results of extensive system trades to achieve a light-weight, high performance satellite design. An overview of experiment objectives, research advances, and satellite design is presented

University Nanosatellite Distributed Satelllite Capabilities to Support TechSat 21

A new way to perform space missions utilizes the concept of clusters of satellites that cooperate to perform the function of a larger, single satellite. Each smaller satellite communicates with the others and shares the processing, communications, and payload or mission functions. The required functionality is thus spread across the satellites in the cluster, the aggregate forming a virtual satellite . The Air Force Research Laboratory (AFRL) initiated the TechSat 21 program to explore the basic technologies required to enable such distributed satellite systems. For this purpose, Space Based Radar (SBR) was selected as a reference mission to help identify technology requirements and to allow an easy comparison to a conventional approach. A summary of the basic mission and the performance requirements is provided. The satellite cluster approach to space missions requires science and technology advances in several key areas. Each of these challenges is described in some detail, with specific stressing requirements driven by the SBR reference mission. These TechSat 21 research and technology areas are being studied in a coordinated effort between several directorates within AFRL and the Air Force Office of Scientific Research. In support of TechSat 21, the Air Force Office of Scientific Research and the Defense Advanced Research Projects Agency are jointly funding 10 universities with grants of $50k/year over two years to design and assemble 10–12 nanosatellites (approx 10kg each) for launch in November 2001. The universities are conducting creative low-cost space experiments to explore the military usefulness of nanosatellites in such areas as formation flying, enhanced communications, miniaturized sensors and thrusters, and attitude control. AFRL is developing a deployment structure and providing advanced microsatellite hardware, and NASA Goddard is providing advanced crosslink communication and navigation hardware and flight algorithms to demonstrate formation flying. Numerous industry partners are also supporting the universities with hardware, design expertise, and test facilities. Areas of particular interest to the TechSat 21 program include autonomous operation and simplified ground control of satellite clusters, intersatellite communications, distributed processing, and formation control. This paper summarizes both hardware and computational challenges that have been identified in both the TechSat 21 and the university nanosatellite programs for implementing operational satellite subsystems to accomplish these tasks

Interferometric Satellite Data in Structural Health Monitoring: An Application to the Effects of the Construction of a Subway Line in the Urban Area of Rome

In recent years, the use of interferometric satellite data for Structural Health Monitoring has experienced a strong development. The urban environment confirms its fragility to adverse natural events, made even more severe by climate change. Hence, the need to carry out continuous monitoring of structures and artefacts appears increasingly urgent. Furthermore, satellite data could considerably increase the feasibility of traditional Structural Health Monitoring (SHM) approaches.This study aims to explore this remote sensing approach, focusing on the representation techniques that can be adopted to highlight their advantages and provide an interpretation of the results. In particular, the study analyzes records from the urban area of Rome (Italy), subject to the construction of a new subway line. These data are exploited to create a velocity map to highlight the possible subsidence phenomenon induced by excavations. Then, the paper focuses on single buildings or building complexes through the entropy–energy representation. Beyond the different limitations caused by the input data, a correlation is identified between the results of the two representation techniques. Accordingly, the effects of excavation on the urban area are demonstrated, and the methodologies are validated

The crustal dynamics intelligent user interface anthology

The National Space Science Data Center (NSSDC) has initiated an Intelligent Data Management (IDM) research effort which has, as one of its components, the development of an Intelligent User Interface (IUI). The intent of the IUI is to develop a friendly and intelligent user interface service based on expert systems and natural language processing technologies. The purpose of such a service is to support the large number of potential scientific and engineering users that have need of space and land-related research and technical data, but have little or no experience in query languages or understanding of the information content or architecture of the databases of interest. This document presents the design concepts, development approach and evaluation of the performance of a prototype IUI system for the Crustal Dynamics Project Database, which was developed using a microcomputer-based expert system tool (M. 1), the natural language query processor THEMIS, and the graphics software system GSS. The IUI design is based on a multiple view representation of a database from both the user and database perspective, with intelligent processes to translate between the views

Enabling Hybrid Architectures and Mesh Network Topologies to Support the Global Multi-Domain Community

The turn of the new decade also represents the dawn of a new shift in domain operations. Concepts such as “Space Dial Tone,” reliable global access to internet, on-demand Earth observation, and remote sensing, while still not fully realized, are no longer purely imaginative. These concepts are in high demand and are coupled with the goals of Global Multi-Domain Operations (MDO). Small satellites (smallsats) have emerged as functionally reliable platforms, driving the development of next-generation satellite constellations. To achieve the potential of tomorrow’s technology, these constellations must embrace space mission architectures based on interoperable, open-system constructs such as hybrid architectures and mesh network topologies. This paper presents the full timeline for realization of multi-node, disparate (sovereign, coalition, commercial, etc.) multi-domain (Space, Air, Maritime, Land, and Cyber) systems to support future space mission architectures. It identifies and discusses the underlying technologies needed to bring new “system-of-systems” concepts to operational capability. Technologies to be discussed include: message-agnostic physical/protocol “Bridges”; Machine-to-Machine (M2M) data sharing enabled through Electronic Data Sheet (EDS) standards; and, new concepts related to Artificial Intelligence (AI) enabled human decision making. Tying these technologies together effectively will positively impact the smallsat market and fundamentally change mission architectures in the near future

Verification of the virtual bandwidth SAR (VB-SAR) scheme for centimetric resolution subsurface imaging from space

This work presents the first experimental demonstration of the virtual bandwidth synthetic aperture radar (VB-SAR) imaging scheme. VB-SAR is a newly-developed subsurface imaging technique which, in stark contrast to traditional close-proximity ground penetrating radar (GPR) schemes, promises imaging from remote standoff platforms such as aircraft and satellites. It specifically exploits the differential interferometric synthetic aperture radar (DInSAR) phase history of a radar wave within a drying soil volume to generate high- resolution vertical maps of the scattering through the soil volume. For this study, a stack of C-band VV polarisation DInSAR images of a sandy soil containing a buried target was collected in the laboratory whilst the soil moisture was varied - firstly during controlled water addition, and then during subsequent drying. The wetting image set established the moisture-phase relationship for the soil, which was then applied to the drying DInSAR image set using the VB-SAR scheme. This allowed retrieval of high resolution VB-SAR imagery with a vertical discrimination of 0.04m from a stack of 1m vertical resolution DInSAR images. This work unequivocally shows that the basic principles of the VB-SAR technique are valid and opens the door to further investigation of this promising technique

Land Use Identification of the Metropolitan Area of Guadalajara Using Bicycle Data: An Unsupervised Classification Approach

El siguiente trabajo propone diferentes maneras de resolver una problemática que se encuentra en la actualidad, que es el hacer la investigación en el área de land-use, mapeo y comportamiento humano evaluando su movimiento por medio de fuentes de información que contienen información geo referenciada, también se comparte la meta de clasificar diferentes secciones y su relación entre ellas. Se utilizó como fuente de información MiBici que es una plataforma de compartimiento de bicicleta que existe en la ciudad de Guadalajara, Jalisco, la cual comparte mes tras mes un archivo consolidado de los viajes que se realizan en cada mes, cabe mencionar que el acceso de esta información es totalmente libre. Las metodologías utilizadas fueron agile para planeación del proyecto, KNN, Decision Trees y KMeans para la cauterización de las zonas, el lenguaje de programación utilizado fue Python, además se anexo una propuesta de implementación utilizando la plataforma de Amazon Web Service con el objetivo de proponer una solución más “sencilla” de implementar, pero con el mismo valor que hacerlo con puros recursos libres. El proceso se dividió primordialmente en 3 partes en donde la primera fue limpiar datos y entenderlos, se aplicaron algoritmos machine learning que fueron Decision tree y KNN, para la segunda etapa evaluando los resultados de la etapa anterior se hicieron modificaciones a los datos en donde se agregaron nuevos campos para mejor los resultados y se aplicó KMeans para la creación de grupos y como último paso se creó un flujo que inicio con la limpieza de los datos en crudo utilizando herramientas de AWS y se terminó con la interpretación de los resultados finales. Los resultados obtenidos fueron demasiados alentadores ya que los grupos que se obtuvieron fueron demasiados marcados y revisándolo con las zonas relacionadas a los nodos se encontró una gran relación. Sin duda alguna queda aún demasiado trabajo a desarrollar en esta rama de investigación

Formation Flying SAR: Analysis of Imaging Performance by Array Theory

This article analyzes the process of image synthesis for a formation flying synthetic aperture radar (FF-SAR), which is a multistatic synthetic aperture radar (SAR) based on a cluster of receiving-only satellites flying in a close formation, in the framework of the array theory. Indeed, the imaging properties of different close receivers, when analyzed as isolated items, are very similar and form the so-called common array. Moreover, the relative positions among the receivers implicitly define a physical array, referred to as spatial diversity array. FF-SAR imaging can be verified as a result of the spatial diversity array weighting the common array. Hence, different approaches to beamforming can be applied to the spatial diversity array to provide the FF-SAR with distinctive capabilities, such as coherent resolution enhancement and high-resolution wide-swath imaging. Simulation examples are discussed which confirm that array theory is a powerful tool to quickly and easily characterize FF-SAR imaging performance

Image Simulation in Remote Sensing

Remote sensing is being actively researched in the fields of environment, military and urban planning through technologies such as monitoring of natural climate phenomena on the earth, land cover classification, and object detection. Recently, satellites equipped with observation cameras of various resolutions were launched, and remote sensing images are acquired by various observation methods including cluster satellites. However, the atmospheric and environmental conditions present in the observed scene degrade the quality of images or interrupt the capture of the Earth's surface information. One method to overcome this is by generating synthetic images through image simulation. Synthetic images can be generated by using statistical or knowledge-based models or by using spectral and optic-based models to create a simulated image in place of the unobtained image at a required time. Various proposed methodologies will provide economical utility in the generation of image learning materials and time series data through image simulation. The 6 published articles cover various topics and applications central to Remote sensing image simulation. Although submission to this Special Issue is now closed, the need for further in-depth research and development related to image simulation of High-spatial and spectral resolution, sensor fusion and colorization remains.I would like to take this opportunity to express my most profound appreciation to the MDPI Book staff, the editorial team of Applied Sciences journal, especially Ms. Nimo Lang, the assistant editor of this Special Issue, talented authors, and professional reviewers